Stress relieved container and method of making same

ABSTRACT

This disclosure relates to a metal container, and more particularly to a thin walled, metal can having a welded side seam and wherein at least one end thereof is necked-in and then outwardly flanged so as to receive an end of a reduced diameter. In order to prevent edge cracking during the flanging operation adjacent the welded seam, the necked-in edge of the can body is provided with a shallow notch on each side of the welded seam. In addition, in order to prevent wrinkling of the metal in alignment with the notches during the necking-in operation and subsequent fracture along the areas of wrinkling during flanging, the end edge portion of the blank from which the can body is formed is provided with stress relief indentations adjacent the notches.

United States Patent Bartels 1 June 20, 1972 [54] STRESS RELIEVEDCONTAINER AND METHOD OF MAKING SAME [72] Inventor: Herbert D. Bartels,Palos Heights, 1]].

[73] Assignee: Continental Can Company, Inc., New

York, NY.

[22] Filed: Jan. 12, 1970 [21] Appl. No.: 2,304

Primary Examiner-M. Henson Wood, Jr. Assistant Examiner-Thomas C. Culp,Jr. Anamey-Diller, Brown, Ramik & Holt ABSTRACT This disclosure relatesto a metal container, and more particularly to a thin walled, metal canhaving a welded side seam and wherein at least one end thereof isnecked-in and then outwardly flanged so as to receive an end of areduced diameter. in order to prevent edge cracking during the flangingoperation adjacent the welded scam, the necked-in edge of the can bodyis provided with a shallow notch on each side of the welded seam. Inaddition, in order to prevent wrinkling of the metal in alignment withthe notches during the necking-in operation and subsequent fracturealong the areas of wrinkling during flanging, the end edge portion ofthe blank from which the can body is formed is provided with stressrelief indentations adjacent the notches.

MChinsJDrawingflgures PATENTEnJum m2 RWR ART /NVNTUR HERBERT D. BHRTELS:MM a AT ;QQNEY.S

STRESS RELIEVED CONTAINER AND METHOD OF MAKING SAME This inventionrelates in general in new and useful improvements in the manufacture ofwelded, thin-walled metal cylinders, and more particularly to thinwalled metal cans having welded side seams wherein one or more ends ofthe can bodies are necked-in prior to flanging.

It has been found in the past that when a thin walled, metal cylinder isprovided with a welded side seam of the overlapping bond type, in orderto permit flanging without fracture of the metal adjacent to the sideseam, it is necessary to provide the end edges of such metal cylinderswith stress relief notches. The customary fractures are known aslongitudinal flange cracks and are caused by circumferential tensilestress. Failure of the metal adjacent to the weld bond, which isinherently weakened by the welding process, is prevented by stressrelief notches adjacent to the overlap of the side seam. The notchesadjacent to the overlap reduce or minimize the circumferential, tensilestress between the notched locations and thereby permit the weldedcylinder to be flanged without failure.

When the welded cylinder is a can body, at times prior to the flangingthereat, the ends are necked-in so as to receive ends of smallerdiameter. The necking-in of the ends is done in a die forming operationwhich reduces the cylinder diameter at each end of the can bodysimultaneously. In the die forming operation, the metal is subjected tointensive circumferential, compressive stress around the circumferenceof the cylinder ends undergoing diameter reduction. The die forming toolrelationship requires that suflicient clearance be allowed toaccommodate the thicker section of the overlapped side seam and toprevent abrasion of protective coatings applied to the metal surfaces inprior operations.

In the die forming, diameter reducing operation, the circumferential,compressive stress causes failure to develop in the metal undergoingdiameter reduction in the form of folds or wrinkles. The folds developand are not removed or ironed out due to the aforementioned toolclearance. The die forming tooling is designed to permit the inner toolto float so that the greatest tool clearance is always generated in thearea of the thicker overlapped bond in the welded cylinder. As aconsequence, the folds or wrinkles are predisposed to occur adjacent tothe overlapped bond. The welded side seam cylinder, which is providedwith the stress relief notches, provides an additional problem 'in thatthe stress relief notches are of necessity located adjacent to theoverlapped bond. The notched areas are then in the primary area in whichcompressive failure occurs and further, provide added probability forfailure to occur, due to the increased discontinuity of thecircumference by the presence of the notches.

The compressive failures identified as folds or wrinkles are not inthemselves considered defects. However, when the cylinder or can body isflanged in the normal die flanging operation, the wrinkled area issubject to fracture to a larger degree than a non-wrinkled area. Theprobability of fracture is increased many times when the wrinkle issuperimposed in the notch itself. This is due to the fact that thestress relief notch acts as a stress riser when subjected to thecircumferential tensile stress and in performing its function as atensile stress relief for the welded overlap, a stress concentration isdeveloped within the notch.

In accordance with this invention, it is proposed to provide acompressive stress relief for the notched areas so that such wrinklingwhich may occur during the necking-in operation will not occur in axialalignment with the notched areas, but adjacent thereto. In this manner,such wrinkling which may occur during the necking-in operation will notoccur in alignment with the notched areas, but adjacent thereto andthereby cracking in alignment with the notched areas has beeneliminated.

In accordance with this invention, it is proposed to provide slightindentations adjacent to the notched areas such that both notches andthe welded side seam lie in between the indentations. The indentations,which are formed by bending the metal from which the cylinder is formed,are in efiect a preformed wrinkle. When the cylinder with theindentations is subjected to the usual circumferential compressivestress of die forming diameter reduction, the indentations developimmediately into failure in the form of folds or wrinkles. Theindentations are predetermined failure points and yield to failurepreferentially to a failure within the notched areas located between theindentations. By developing into failures under circumferential,compressive stress the indentations are effectively providingcompressive stress relief for the metal in the immediate vicinity.

With the above and other objects in view that will hereinafter appear,the nature of the invention will be more clearly understood by referenceto the following detailed description, the appended claims and theseveral views illustrated in the accompanying drawing.

IN THE DRAWING:

FIG. 1 is a fragmentary elevational view showing one end of a weldedcylinder having stress relief notches on the opposite sides of thewelded side seams thereof.

FIG. 2 is a fragmentary elevational view similar to FIG. 1 and shows theend of the metal cylinder necked-in with the subsequent folding orwrinkling of the metal in alignment with the stress relief notches. 7

FIG. 3 is a fragmentary elevational view similar to FIG. 1 showing thenecked-in cylinder after outward flanging thereof with the resultantcracking along the loosely formed wrinkles or folds in alignment withthe stress relief notches.

FIG. 4 is an enlarged fragmentary perspective view of one comer portionof a blank from which the metal cylinder is formed, the blank beingprovided with a stress relief indentation in the edge portion thereofimmediately adjacent to the stress relief notch.

FIG. 5 is a fragmentary elevational view similar to FIG. I of a weldedside seam cylinder formed with the blank of FIG. 4.

FIG. 6 is a fragmentary elevational view similar to FIG. 2 and shows thecylinder of FIG. 5 after the necking-in operation.

FIG. 7 is a fragmentary elevational view similar to FIG. 3 and shows thecylinder of FIG. 6 afier a subsequent flanging operation.

Referring now to the drawing in detail, reference is first made to theprior art showings of FIGS. 1, 2 and 3. As previously described, thereis illustrated in FIG. I a welded cylinder, which is generallyidentified by the numeral 10. The welded cylinder is formed ofrelatively thin sheet metal having a thickness preferably on the orderof 0.008 inch and varying generally from 0.004 to 0.011 inch. The metalcylinder 10 is provided with a welded side seam 11 having an overlappingbond. The cylinder 10 is formed from a flat blank with the end edgesthereof being provided with stress relief notches 12 adjacent thelongitudinal edges thereof prior to the shaping thereof to thecylindrical form and the formation of the welded side seam 11.

Referring now to FIG. 2, it will be seen that the extreme end of themetal cylinder 10 has been necked-in in the manner previously describedto provide an extreme end portion 13 of a reduced diameter. During thenecking-in operation, there has been compressive failure of the metal ofthe extreme end portion with wrinkling or folding occurring in alignmentwith the stress relief notches 12 as at 14.

Referring now to FIG. 3, it will be seen that there is illustratcd themetal cylinder 10 afier an end flanging operation wherein the necked-inend portion 13 is provided with an outwardly directed circumferentialflange 15 of the type normally required to facilitate the seaming of anend to the metal cylinder, preferably by means of a customarydouble-seaming operation. In the flanging operation, the necked-in endportion 13 is tensile stressed with the result that the stress reliefnotches 12 form stress rises in alignment with the previously formedwrinkles or folds 14 and tensile failure occurs in the form of cracks16. The cracks 16 prevent the forming of a sealed seam between the metalcylinder or container body in a conventional container end (not shown).

Referring now to FIG. 4 in particular, it will be seen that there isillustrated a portion of a blank 17 from which a metal cylinder orcontainer body, such as the cylinder 10, may be formed. The blank 17 isgenerally rectangular in outline and includes a longitudinal edge 18 andan end edge 20. The blank 17 is provided with a stress relief notch 12in the end edge 20 thereof adjacent each of the longitudinal edges 18 inthe manner previously described.

In accordance with this invention, the blank 17 is also provided with astress relief indentation 21. The stress relief in dentation 21 isformed by bending or creasing the metal of the blank 17 immediatelyadjacent to the respective stress relief notch so as to effectively forma pre-formed wrinkle or fold. it is to be noted that the stress reliefindentation 21 is preferably located at a distance of approximatelyone-eighth inch from the nearest portion of the associated stress reliefnotch 12 and has a depth of approximately 0.020 inch or less with a spanof approximately one-eighth inch.

Reference is now made to FIG. wherein there is illustrated a cylinder 22which is formed from the blank 17 in the same manner as was the cylinder10. The cylinder 22 is provided with the customary overlapped bondwelded side seam 11 at each end thereof which is to be subsequentlynecked-in in the manner illustrated in FIG. 2 is provided with thestress relief notches 12 on opposite sides of the side seam 11. Inaddition, adjacent each of the stress relief notches 12 there is one ofthe stress relief indentations 21, the stress relief notches 12 and thewelded side seam 11 lying between the stress relief indentations 21.

Referring next to FIG. 6, it will be seen that the cylinder 22 has had anecking-in operation performed on the illustrated end thereof to definea necked-in end portion 23 in the manner previously described withrespect to FIG. 2. During the necking-iii operation, there has beencontrolled failure of the end portion 23 in the form of folds orwrinkles 24. However, due to the formation of the stress reliefindentations 21, the wrinkles or folds 24 are formed outside of the areaof the stress relief notches 12. As previously indicated, the stressrelief indentations 21 are disposed approximately one-eighth inch fromthe stress relief notches 12. The location of the stress reliefindentations is preferably close to the stress relief notches formaximum effect, but sufficiently removed therefrom to prevent theintended indentation failure to en compass the stress relief notches.

Referring now to FIG. 7 in particular, it will be seen that the metalcylinder 22 has had a circumferential flanging operation performed onthe necked-in end portion 23 thereof so as to define a circumferentialflange 25 for the purpose of securing I to the end of the cylinder 22 aconventional end closure, as

described with respect to FIG. 3. During this flanging operation, thenecked-in end portion 23 is tensile stressed with the result that thepreviously formed folds or wrinkles 24 in the area of the stress reliefindentations 21 now appear as minor residual wrinkles 26 which in no wayaffect the satisfactory seaming of a conventional end closure to thecylinder 22. It is to be noted that no flange cracking has occurredduring the flanging operation.

Although it was the initial concept of this invention to prevent flangecracking in the manner discussed hereinabove, it has been found that theprovision of the stress relief indentations 21, which form the folds orwrinkles 24 during the necking-in operation, also function to relievecompressive shear stresses in the bond of the side seam. While therelieving or partial relieving of the compressive shear stresses in thebond of the side seam is advantageous where the bond is a welded bond,it has been found that this relieving of compressive shear stresses isparticularly advantageous in tubular bodies wherein the side seam is ofthe type having a cemented or soldered bond.

In view of the foregoing, although the invention has been specificallydescribed and illustrated in relation to a tubular body having a weldedside seam and wherein at least one end edge thereof is notched onopposite sides of the side seam to prevent crashing during a flangingoperation, the invention is not so limited, and may be utilized inconjunction with tubular bodies having bonded side seams wherein atleast one end of a tubular body is to be necked-in and whereincompressive shear stresses resulting from the necking-in operation mayunduly weaken or rupture the bonded side seam. A stated above, the bondof the side seam may be a welded bond, a cemented bond or a solderedbond.

At this time, it is pointed out that although reference has beengenerally made to a metal cylinder and in some instances to a metalcontainer, the invention is particularly adaptable to the manufacture ofcan bodies of all sizes, including can bodies having a diameter underthree inches such as normally utilized in the packaging of beer and softdrinks.

It is also pointed out that although the illustrated configuration ofthe stress relief indentation is that of a generally conical outline,the invention is not restricted to this specific outline. Although apreferred embodiment of the invention has been specifically illustratedand described herein it is to be understood that minor variations may bemade in the shape, size and location of the stress relief indentationswithout departing from the spirit and scope of the invention, as definedby the appended claims.

I claim:

1. A tubular body having a welded side seam, at least one end of saidcan body having formed in the respective end edge thereof a stressrelief notch on each side of said side seam, and stress relief meansformed in said end edge portion on each side of said seam and adjacent arespective one of said stress relief notches.

2. The body of claim 1 wherein said stress relief means is in the formof a shallow indentation opening through the end edge.

3. The body of claim 1 wherein said stress relief means is in the formof a shallow indentation opening through the end edge, said indentationbeing tapered and of a maximum width and depth at said end edge.

4. The body of claim 1 wherein said stress relief means is in the formof a shallow indentation opening through the end edge, said indentationbeing tapered and of a maximum width and depth at said end edge, saiddepth being on the order of 0.020 inch.

The body of claim 1 wherein each said stress relief means is disposed onthe side of a respective one of said stress relief notches remote fromsaid side seam.

6. The body of claim 1 wherein each said stress relief means is disposedon the side of a respective one of said stress relief notches remotefrom said side seam and is spaced therefrom on the order of one-eighthinch.

7. The body of claim 1 wherein said one end is necked-in and said stressrelief means is in the form of a controlled wrinkle.

8. The body of claim 1 wherein said body in a container body, said oneend is necked-in and flanged, and said stress relief means is in theform of a minor residual wrinkle.

9. The can body of claim 1 wherein said can body is formed from a blankand said blank contains said stress relief means.

10. A tubular body having a bonded overlapping side seam of which oneend is necked-in under compression, said tubular body one end havingstress relief means on each side of said side seam partially absorbingcompressive shear stresses in said side seam, said stress relief meansbeing in the form of controlled wrinkles.

11. The tubular body of claim 10 wherein said controlled wrinkles openthrough an end edge of the tubular body.

12. The tubular body of claim 10 wherein said controlled wrinkles openthrough an end edge of the tubular body with each wrinkle resulting froma shallow indentation formed in said tubular body one end prior to thenecking-in of said tubular body one end.

13. The tubular body of claim 12 wherein said tubular body is formedfrom a blank and said blank contains said indentations.

14. The tubular body of claim 12 wherein said necked-in end is outwardlyflanged for the securement of an end member 5 to said tubular body andsaid indentations are in the form of minor residual wrinkles in saidflange.

1. A tubular body having a welded side seam, at least one end of saidcan body having formed in the respective end edge thereof a stressrelief notch on each side of said side seam, and stress relief meansformed in said end edge portion on each side of said side seam andadjacent a respective one of said stress relief notches.
 2. The body ofclaim 1 wherein said stress relief means is in the form of a shallowindentation opening through the end edge.
 3. The body of claim 1 whereinsaid stress relief means is in the form of a shallow indentation openingtHrough the end edge, said indentation being tapered and of a maximumwidth and depth at said end edge.
 4. The body of claim 1 wherein saidstress relief means is in the form of a shallow indentation openingthrough the end edge, said indentation being tapered and of a maximumwidth and depth at said end edge, said depth being on the order of 0.020inch.
 5. The body of claim 1 wherein each said stress relief means isdisposed on the side of a respective one of said stress relief notchesremote from said side seam.
 6. The body of claim 1 wherein each saidstress relief means is disposed on the side of a respective one of saidstress relief notches remote from said side seam and is spaced therefromon the order of one-eighth inch.
 7. The body of claim 1 wherein said oneend is necked-in and said stress relief means is in the form of acontrolled wrinkle.
 8. The body of claim 1 wherein said body in acontainer body, said one end is necked-in and flanged, and said stressrelief means is in the form of a minor residual wrinkle.
 9. The can bodyof claim 1 wherein said can body is formed from a blank and said blankcontains said stress relief means.
 10. A tubular body having a bondedoverlapping side seam of which one end is necked-in under compression,said tubular body one end having stress relief means on each side ofsaid side seam partially absorbing compressive shear stresses in saidside seam, said stress relief means being in the form of controlledwrinkles.
 11. The tubular body of claim 10 wherein said controlledwrinkles open through an end edge of the tubular body.
 12. The tubularbody of claim 10 wherein said controlled wrinkles open through an endedge of the tubular body with each wrinkle resulting from a shallowindentation formed in said tubular body one end prior to the necking-inof said tubular body one end.
 13. The tubular body of claim 12 whereinsaid tubular body is formed from a blank and said blank contains saidindentations.
 14. The tubular body of claim 12 wherein said necked-inend is outwardly flanged for the securement of an end member to saidtubular body and said indentations are in the form of minor residualwrinkles in said flange.